Sensor device for use in a medical fluid delivery system

ABSTRACT

A sensor device for use in a medical fluid delivery system, or an infusion pump device, comprises a fluidic chamber with a deformable cover closing at least an area of the chamber and an optical detection system comprising at least one light emitter for emitting one or more incident light beams and a sensor unit for monitoring one or more reflected light beams is presented. In a pressurized state of the fluidic chamber, the deformable cover is deformed such that it forms an inflexion point area within the deformed cover. The one or more incident light beams emitted by the light emitter are directed on the cover such that the one or more incident light beams are reflected essentially in the inflexion point area.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of PCT/EP2012/055072, filed Mar. 22,2012, which is based on and claims priority to EP 11159202.8, filed Mar.22, 2011, which is hereby incorporated by reference.

BACKGROUND

The present disclosure generally relates to a sensor device for use in amedical fluid delivery system and, in particular, to an infusion pumpsdevice, like an insulin infusion pump device, to monitor a fluidicpressure and/or detecting occlusions in a fluidic system of such systemand device.

Medical fluid delivery systems for the administration of, for example,liquid medical fluids, such as infusion pump devices, are often usedwith patients who have a continuous, and in the course of the dayvarying, need of a medicine that can be administered, for example, bysubcutaneous infusion. Specific applications are, for example, certainpain therapies and the treatment of diabetes. In such cases, computercontrolled automated infusion pump devices are used, which can becarried by the patient on the body, and which contain a certain amountof liquid medicine in a medicine reservoir. The liquid medicine issupplied to the patient's body from the medicine reservoir through afluidic system to an infusion cannula or an injection needle. Mostlysuch medical fluid delivery systems comprise a reusable unit includingan actuation mechanism, a dosing mechanism, electronics for controllingthe mechanisms, and the like and a disposable unit including, forexample, a fluid reservoir, which is discarded after emptying thereservoir.

The liquid medicine can be obtained by a downstream pump from a flexiblecontainer. Flexible containers have the advantage of a smaller volumesurplus of the container in relation to its content reducing themanufacturing costs and enabling design of infusion pump devices ofsmaller overall dimensions. Thus, the device cannot be seen throughclothing and can be carried as comfortably as possible.

In the context of liquid medicine administration via an infusion pumpdevice, sensor devices are used for controlling the dosing, monitoringthe correct operation of the system, and for fast detection of faultsand hazards, such as occluded infusion lines or cannulae, emptycontainers, or malfunctioning pump systems. A pressure sensor device maybe in a fluid path downstream of a pump device and upstream of aninfusion cannula.

Such pressure sensor devices typically comprise a micro-fluidic chamberfilled with liquid and fluidly connected to the fluidic system. Thechamber is covered by a flexible, resilient membrane such that apressure difference between the fluidic pressure inside the sensorchamber and the outside (such as atmospheric) pressure will temporarilydeform the membrane. The resulting deflection of the membrane can thenbe measured in order to determine the internal pressure of the fluidicsystem.

A suitable approach to measure the deformation of the membrane isoptical detection of a light beam reflected on the membrane. Thepressure sensor device includes a micro-fluidic chamber connected to afluidic system comprising a rigid bottom substrate and a flexible,resilient top cover, for example, a membrane. An optical detectionsystem measures a deformation of the cover membrane by determining theinteraction of a light beam with the cover membrane. For that purpose, alight emitting device, such as, a laser diode, directs a light beam at acertain angle onto the surface of the cover membrane where it isreflected. The pressure difference between the inner volume of themicro-fluidic chamber and the outer environment acts on the covermembrane and deforms it to a certain extent depending on the pressuredifference. As a result, the angle of the reflected light beam changesand the beam is transversely shifted. By monitoring the position of thereflected light beam, the deformation of the cover membrane can bemeasured and based on the obtained results a pressure difference valuecan be determined.

In one example, an insulin pump comprises a reusable unit with drive,dosing and controlling systems and a disposable unit with a flow pathand a catheter tube. The flow path can be connected to the driving anddosing mechanism such that a liquid system runs from a liquid reservoirto the catheter tube. A resilient membrane is in the flow path andcovers a fluidic chamber. The membrane is impinged directly by theliquid in the flow path such that it is deflected towards the reusableunit in case of a pressure increase, for example, due to an occlusion ofthe liquid system. The reusable unit comprises a light emitter in formof a laser diode and a photosensitive x-y sensor connected to thecontrolling system. The light beam of the laser diode can be directed ona rigid reflector arranged on the membrane. Alternatively, the lightbeam can be directed directly on the membrane surface. In this case, asmall area on the surface of the membrane is metal-coated to providegood reflecting properties of the membrane. The incident light beam isfocused on an area of the membrane at a distance to the center of themembrane. That means in a deflected state of the membrane the reflectingarea is inclined and rounded with respect to the non-deflected state.Therefore, a reflected light beam changes direction and shape, which canbe detected by the x-y sensor and is an indication for a pressure changewithin the liquid system.

Another infusion pump system comprises an occlusion sensor that can beused to detect when an occlusion exists in the fluid path between amedicine reservoir and the infusion site. The occlusion sensor includesa flexible membrane which can be deflected by rising pressure in thefluid path such that it touches a wall of an air cavity. The incidentmeasurement light beam is guided through a light transmissive member tothe air cavity. In a non-deflected state, the incident beam is totallyreflected at the air cavity. In a deflected state, when the membranetouches the air cavity, reduced reflection occurs. The reduction of theintensity of the reflected light beam is a measurement for the pressurein the fluid path.

Since some of the parts of the pressure sensor device are in thedisposable unit and other parts are in the reusable unit, theorientation of disposable and reusable part towards each other can be acritical parameter of reliable measuring results. In the known systems,the tolerances between these units must be as small as possible. Formonitoring the reflected light beam in a pressure sensor according tothe prior art, a detector in the optical detection system often isdesigned to be movable, or a multiplicity of detectors at differentpositions and at different angles are included in the device. Both ofthese aspects make such sensor devices expensive and difficult to make.A wide range of directions of reflected light beams due to the largevariety or diffuse reflection angles on a membrane also requires acomplex sensor array in the pressure sensor device.

Therefore, there is a need to provide an improved sensor device for usein a medical fluid delivery system, such as an infusion pump device forliquid medicines, like insulin, for monitoring pressure variations in amedical fluid delivery system, which is easy to install and indicatespressure changes or fluid path occlusion in a simple manner and overcomethe drawbacks of prior art devices.

SUMMARY

According to the present disclosure, a sensor device for use in amedical fluid delivery system is disclosed. The sensor device cancomprise a fluidic chamber with a deformable cover closing at least anarea of the fluidic chamber, wherein, in a pressurized state of thefluidic chamber, the deformable cover can be deformed such that it canform an inflexion point area within the deformed cover and an opticaldetection system comprising at least one light emitter for emitting oneor more incident light beams and a sensor unit for monitoring one ormore reflected light beams, wherein the one or more incident light beamsemitted by the light emitter can be directed on the cover such that theone or more incident light beams can be reflected in the inflexion pointarea.

In accordance with one embodiment of the present disclosure, a methodfor monitoring a pressure change in a fluidic chamber of a medical fluiddelivery system using a sensor device id disclosed. The method cancomprise directing one or more incident light beams on the inflexionpoint area of the deformable cover; detecting one or more reflectedlight beams reflected from the deformable cover in a non-pressurizedstate and a pressurized state; and comparing detection data of thenon-pressurized state and the pressurized state to extract the pressurechange value.

Accordingly, it is a feature of the embodiments of the presentdisclosure to provide an improved sensor device for use in a medicalfluid delivery system, such as an infusion pump device for liquidmedicine, like insulin, for monitoring pressure variations in a medicalfluid delivery system, which is easy to install and indicates pressurechanges or fluid path occlusion in a simple manner and overcome thedrawbacks of prior art devices. Other features of the embodiments of thepresent disclosure will be apparent in light of the description of thedisclosure embodied herein.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The following detailed description of specific embodiments of thepresent disclosure can be best understood when read in conjunction withthe following drawings, where like structure is indicated with likereference numerals and in which:

FIG. 1 a illustrates a schematic cross-sectional view of a sensor devicein a non-pressurized state according to an embodiment of the presentdisclosure.

FIG. 1 b illustrates a schematic cross-sectional view of the sensordevice according to FIG. 1 a in a pressurized state according to anembodiment of the present disclosure.

FIG. 2 a illustrates schematically a translational offset of the coverin a pressurized state according to an embodiment of the presentdisclosure.

FIG. 2 b illustrates schematically an inclination of the cover in apressurized state according to an embodiment of the present disclosure.

FIG. 2 c illustrates schematically a superposition of the translationaloffset and the an inclination of the cover in a pressurized stateaccording to an embodiment of the present disclosure.

FIG. 3 a illustrates a diagram of sensor signals of a sensor deviceusing sensor unit comprising a dual-element sensor according to anembodiment of the present disclosure.

FIG. 3 b illustrates a diagram of an algorithm to determine a thresholdpressure value in accordance to a reference pressure value according toan embodiment of the present disclosure.

FIG. 4 illustrates schematically a first embodiment of a sensor deviceusing optical elements to direct incident and reflected light beamsaccording to an embodiment of the present disclosure.

FIG. 5 illustrates schematically a second embodiment of a sensor deviceusing optical elements according to an embodiment of the presentdisclosure.

FIG. 6 illustrates schematically a third embodiment of a sensor deviceusing optical elements according to an embodiment of the presentdisclosure.

FIG. 7 illustrates schematically a fourth embodiment of a sensor deviceusing optical elements for splitting reflected light beams according toan embodiment of the present disclosure.

FIG. 8 illustrates schematically a fifth embodiment of a sensor deviceusing optical elements for splitting reflected light beams according toan embodiment of the present disclosure.

FIG. 9 illustrates a schematic cross-sectional view of a firstembodiment of a covering of a disposable unit of a medical fluiddelivery system comprising optical elements to direct incident andreflected light beams according to an embodiment of the presentdisclosure.

FIG. 10 illustrates a schematic cross-sectional view of a secondembodiment of a covering of a disposable unit of a medical fluiddelivery system comprising optical elements according to an embodimentof the present disclosure.

DETAILED DESCRIPTION

In the following detailed description of the embodiments, reference ismade to the accompanying drawings that form a part hereof, and in whichare shown by way of illustration, and not by way of limitation, specificembodiments in which the disclosure may be practiced. It is to beunderstood that other embodiments may be utilized and that logical,mechanical and electrical changes may be made without departing from thespirit and scope of the present disclosure.

A sensor device according to the present disclosure for use in a medicalfluid delivery system can comprise a fluidic chamber with a deformablecover closing at least an area of the chamber and an optical detectionsystem comprising at least one light emitter for emitting one or moreincident light beams and a sensor unit for monitoring one or morereflected light beams. In a pressurized state of the fluidic chamber,the deformable cover can be deformed such that it can form an inflexionpoint area within the deformed cover. The one or more incident lightbeams emitted by the light emitter can be directed on the cover suchthat the one or more incident light beams can be reflected essentiallyin the inflexion point area.

The fluidic chamber can be part of a fluid path of an infusion pumpdevice or a medical fluid delivery system. It can be formed, forexample, as a micro-fluidic chamber in fluidic connection with such afluid path. The cover can be placed over an opening in the fluidicchamber such that the cover can be in contact with the interioratmosphere of the chamber. Advantageously, the cover can cover an atleast partially rounded opening of the fluidic chamber. The cover may bein direct contact with a fluid delivered through the fluidic chamber.But in general, it can be possible to locate a transmission volume, likea gas volume, between the fluid and the cover which can transmitpressure changes in the fluid to the cover.

In one embodiment, the fluidic chamber can be part of a disposable unitof a medical fluid delivery system and the optical detection system canbe part of a reusable unit of the medical fluid delivery system. Thelight emitter can be for example, one or more light emitting diodes(LED) or laser diodes. Advantageously, one diode emitting one light beamof one wavelength can be enough to realize the sensor device. The sensorunit can for example be photodiodes.

The cover can be a flexible, resilient membrane cover which can bedeformable or deflectable. In a normal state of operation of the sensordevice or the medical fluid delivery device, i.e., a regular pressureatmosphere within the fluidic chamber, the cover in general can beessentially not deformed. In the case of a medical fluid delivery systemfor insulin, regular pressure can be about 200 to 2000 mbar relativepressure. This state can be a non-pressurized state of the fluidicchamber, although a specific normal pressure can always exist in thesystem. The non-pressurized state can be determined by a referencemeasurement with the optical detection system. Thus the non-pressurizedstate may serve as a reference state and pressure changes can bedetected in respect to this reference state. In the case where thepressure within the fluidic chamber increases or decreases, the covercan be deformed due to the force of the pressure change. This state canbe a pressurized state of the fluidic chamber comprising a deformedcover.

The inflexion point area can be the area where the radius of curvatureof the cover can change along a line running within the cover from anedge of the cover connected to the fluidic chamber to the center of thecover. It can also be the area within the absolute value of thecurvature changes sign. In this area, the curvature of the cover can benegligible and can act as an even or nearly even reflection area. Infact, when the cover is deformed and buckling to one or the other side,an inflexion line around the center of the cover can be formed.

The one or more incident light beams can be directed on the cover at anangle α. In the normal state of the cover, i.e. the non-pressurizedstate, the incident light beam can meet the cover in an areacorresponding to a potential inflexion point, or in close vicinity ofthis area. While the fluidic chamber can be pressurized to a pressurizedstate that area can be tilted and mostly also offset translativecompared to the normal state due to the deformation of the cover. Sincethe area can comprise the inflexion point, it can be approximately evenand may act as plane reflection area for the incident light beam in thepressurized state. At the same time, it can be the area with the mostangular change compared to the normal state of the cover. That can meanthe one or more light beams can be reflected in the area of the covercomprising the largest change of orientation towards the incident lightbeams when passing from the non-pressurized state to the pressurizedstate. But around the inflexion point there can be a minimum sphericitynegatively affecting the quality of the reflected light beam.

The sensor device can allow a maximum change in reflection of the one ormore incident light beams in the pressurized state compared to thenon-pressurized state of the cover and therefore can ensure accurateobservation of pressure abnormalities within the fluidic chamber. Thedetection at the maximum deflection of the reflected light beams canenable a simple and cost-efficient construction of the sensor unit andcan provide large flexibility in the arrangement of the elements of thesensor device relative to each other.

Good results can be achieved by using an incident light beam, which canessentially be a parallel light beam. Therefore, a laser diode, or alight emitting diode, comprising an optical element for parallelizingemitted light beams can be used advantageously. In the case of aparallel incident light beam and the fact that the deformed cover can begenerally planar in the inflexion point area, the reflected light beamcan also be basically parallel and can be focused precisely towards thesensor unit.

Depending on the light emitter used, the incident light beam maypractically be a bundle of light beams, which can cover not only a pointon the cover but can rather spread over an area on the cover surface.The diameter of the overall incident light beam can be selected suchthat an edge of the beam does not extend beyond the center point of thecover on the fluidic chamber. The diameter of the incident light beammay be about ⅓ or less of the cover diameter. It can be advantageous ifit is less than about ¼ and even less than about ⅕ of the coverdiameter.

In a non-pressurized state of the fluidic chamber, the one or moreincident light beams can be directed on the cover at an angle α.Alternatively, the incident light beams may be focused perpendicular ona non-pressurized cover. An angled direction can provide largeflexibility in the construction of the single elements of the opticaldetection system. Furthermore, it can be advantageous to reflect the oneor more incident light beams at an inflection point area on the coverlocated closest to the light emitter. That can minimize the optical pathof the incident light beam and can maximize the optical path of thereflected light beam from the inflection point area to the sensor unit.Therefore, the distance travelled by the reflecting light beam on thesensor unit can be maximized and the resolution of the sensor unit canbe optimized.

Due to the optimized deflection of the incident light beams by theinflexion point area of the fluid chamber cover, it may not be necessaryto provide a sensor unit with a large array of photodiodes. In oneembodiment, the sensor unit can be a dual-element sensor comprising twophoto-elements. For example, two photodiodes can be directly next toeach other in one line. The incident light beam can be focused on afirst photodiode, when the fluidic chamber is in a non-pressurizedstate, and can be focused on a second photodiode, when the fluidicchamber is in a pressurized state. That can mean when a pressure changein the fluidic chamber occurs, the reflected light beam can wander fromthe first photodiode to the second photodiode. From a particularpressure value on the reflected light beam can be fully focused on thesecond photodiode. The particular pressure value can correspond to aspecific application of the sensor device. For the use of the sensordevice as a pressure sensor, for example, in an infusion pump device,the reflected light beam can change from first to second photodiodewithin a range of pressure change of about 200 mbar to about 2000 mbar.Also, the material of the cover, or the arrangement of the twophotodiodes, may be relevant pressure changes and the particularpressure value respectively.

Alternatively, the two photodiodes may be separate from each other. Inthis case, at least one optical element may be provided in an opticalpath from the inflexion point area towards one or both of a first and/ora second photodiode to direct the reflected light beam to the respectivephotodiode. The optical element or elements can be located such that ina non-pressurized state, the reflected light beam can hit the firstphotodiode directly or a first optical element can direct the beam tothe first photodiode. In a pressurized state, the reflected light beamcan be deflected by the inflexion point area of the cover such that itcan move away from the first photodiode, or the first optical element,and instead can hit a second optical element which guides the beam tothe second photodiode or can meet the second photodiode directly. Amirror element can for example be used to guide the reflected lightbeam.

In one embodiment, the light emitter of the sensor device can be locatedon a side of the cover which is curved in a convex manner in anincreased pressure state of the fluidic chamber. That can mean the lightemitter can direct the one or more incident light beams directly on thecover instead of first passing the interior of the fluidic chamber andthe fluid delivered through the chamber. Advantageously, one side of thecover can be in fluid contact and the light emitter can be located onthe other side of the cover. In this arrangement, the point of incidenceof the incident light beam, which can define the inflexion point area onthe cover, can be subject to a superposition of two effects when thecover changes from the normal state to the pressurized state and shapingthe inflexion point or line as mentioned above. First the point ofincidence can be elevated translational by a distance w and second thepoint of incidence can be tilted by an angle ε. That can mean, in thedeformed state of the cover, the inflexion point area can change itsangular and its translational location in respect to the non-deformedstate. A distance s travelled on the sensor unit by the reflected lightbeams, for example, from the first photodiode to the second photodiode,can therefore be determined by the superposition in case of smallelevation and deflection:s=2·w·cos (α)+d·tan (2ε),wherein α can be defined by the angle of incidence between the incidentlight beam and the cover and d can be the distance from the point ofincidence on the cover to sensor unit. The angle α may lie between about30° to about 60° and even between about 40° to about 50°. In this range,the distance s can act basically linear to a pressure within the fluidicchamber.

Of course, the degree of tilting and elevation can depend on thematerial used for the cover or membrane cover respectively. The covercan be realized as a polymer foil. The polymer foil may be an integralpart of the disposable unit of a delivery device or the like. Materialused can be, for example, PMMA, PC, PET, PA, PSU, or COC/COP. Thethickness of the cover material can be, for example, between about 50 μmand about 200 μm. In another embodiment, the cover material can bebetween about 80 μm and about 150 μm. The cover can reflect a sufficientportion of the incident light beam from the light emitter. Therefore,the cover material can be metalized, for example, by a layer ofaluminium, chrome, silver, gold or the like. Alternatively, a metal foilcomprising sufficient elasticity may be used.

According to another embodiment, an infusion pump device for use in amedical fluid delivery system can comprise a sensor device as mentionedabove. The sensor device may be an integral part of a dosing unit of theinfusion pump device. For example, the fluidic chamber of the sensordevice can be part of a dispensing fluid path connected to a deliveryopening of the infusion pump device.

According to yet another embodiment, a medical fluid delivery device cancomprise a sensor device or an infusion pump device as mentioned above.The delivery device may comprise a reusable unit in combination with adisposable unit. The disposable unit can comprise, for example, a fluidreservoir and usually can be discarded after use. The reusable unit canbe designed so that a disposable unit can be connected to it. Also thesensor unit may be located in the reusable unit. Advantageously, theoptical detection system of the sensor device can be part of thereusable unit of the delivery device and the fluidic chamber can be partof the disposable unit of the delivery device. The disposable unit maycomprise an optical element for directing the incident light beam in apredetermined angle α on the inflexion point area of the cover. That canmean the light emitter can be arranged in any suitable manner relativeto the fluidic chamber and the cover respectively, for example, suchthat the emitted light can be orientated parallel or perpendicular tothe cover. The parallel or perpendicular light beam can be refracted bythe optical element such that light beam can be directed to the cover inthe desired angle α. Furthermore, the disposable unit of the deliverydevice may comprise an optical element for directing the reflected lightfrom the inflexion point area to the sensor unit.

In one embodiment of the medical fluid delivery device, the opticalelements for the light path of the incident and/or reflected light beamsmay be part of the disposable unit of the delivery device. For example,the optical elements may be part of a cap or covering of the fluidicchamber, which can be attached to a surrounding edge of the cover of thefluidic chamber. The optical elements can be transparent for the lightof the light emitter. The optical elements can be made of amorphouspolymer material, for example. The fluidic chamber and the opticalelements may be made of the same material. With the use of such adisposable unit, the incident light beam of the light emitter can beorientated perpendicular to the cover on the fluidic chamber. Theperpendicular light beam can be deflected by the first optical elementor the covering of the disposable unit such that the incident light beamcan be directed in angle α on the inflexion point area of the cover.After reflection of the light beam, a second optical element may focusthe reflected beam onto the sensor unit or one of the photodiodes of thesensor unit respectively.

The use of optical elements can facilitate a correct positioning of thedisposable and reusable units relative to each other. The opticalelements can compensate a mismatch of the units within a tolerance ofapproximately ±0.5 mm. Therefore, a medical fluid delivery systemcomprising a sensor device can enable accurate observation of thefunctioning of the delivery system.

A pressure change in a fluidic chamber of a medical fluid deliverysystem can be monitored using a sensor device by directing one or moreincident light beams on the inflexion point area of the deformablecover. One or more light beams reflected from the deformable cover in anon-pressurized state and a pressurized state can be detected. Thedetection data of the non-pressurized state and the pressurized statecan be compared to extract the pressure change value. Therefore, theoptical detection system can be connected to an electronic controllingsystem of the medical fluid delivery system. A threshold pressure levelcan be defined and deposited in the controlling system at which thedelivery system can be shut down or an alarm can be given to indicate acritical pressure value or malfunction of the system. In the case of anocclusion in a fluidic path of the medical fluid delivery system, thethreshold value may be between about 200 mbar and about 2000 mbarrelative to the atmosphere. However, mostly it can be between about 500mbar and about 1200 mbar and it even can be around 1000 mbar.

In a non-pressurized state of the fluidic chamber, a reflected lightbeam reflected from the non-deformed cover of the fluidic chamber can bedirected on a first photo-element of the dual-element sensor and in apressurized state of the fluidic chamber a reflected light beamreflected from the deformed cover can be directed on a secondphoto-element of the dual-element sensor. The threshold pressure levelmay be reached as soon as the reflected beam fully left the firstphoto-element and fully hits the second photo-element. Alternatively,the threshold pressure level may be achieved as soon as a particularvalue of light intensity is detected on the second photo-element. In astill further alternative, the difference of the light intensitydetected by the two photo-elements can be evaluated.

The sensor device can offer reliable and simple detection of pressurechanges and/or occlusion in a fluid path of the system. It can allow aspace saving structure of a delivery system and can reduce complexity ofdetection algorithms. Also the sensor device can easily and safely beused in combination with reusable and disposable units of the system andcan be produced cost-efficiently.

Referring initially to FIGS. 1 to 10, the basic elements and thefunction of a sensor device and a method for monitoring pressure changesin an infusion pump device and a medical fluid delivery system areexplained with reference to schematic illustrations showing features ofthe disclosure.

FIG. 1 a shows a schematic cross-sectional view of a sensor device foruse in a medical fluid delivery system. The sensor device can comprisesa fluidic chamber 1 with a deformable cover 2 closing at least an areaof the chamber. An optical detection system of the sensor device cancomprise a light emitter 3, such as an LED for example, for emittingincident light beams or a bundle of light beams 4 and a sensor unit 5for monitoring one or more reflected light beams 6. An optional opticalelement 7, such as, a collective lens, an aperture, or the like, can bearranged in the light path of the incident light beam 4 to parallelizethe emitted light of the LED 3. The sensor unit 5, for example, adual-element sensor, can comprise a first photodiode 5 a and a secondphotodiode 5 b arranged directly next to each other. The opticaldetection system can be in a reusable unit of a medical fluid deliverysystem wherein the incident light beam and the reflected light beam canpass through an optical window 8 of the reusable unit to the exterior ofthe reusable unit.

The fluidic chamber 1 can be part of a fluidic module 9 comprising acavity, which can be covered by the deformable cover 2 on one side. Thefluidic chamber 1 can be a microfluidic chamber. A fluid inlet 10 canconnect the fluidic chamber 1 to a fluid reservoir (not shown) and afluid outlet 11 can lead from the fluidic chamber 1 to a patient. Thefluid inlet 10, the fluidic chamber 1 and the fluid outlet 11 can bepart of a fluidic path leading from the fluid reservoir to the patient.The cover may be, for example, glued or welded to the surface of thefluidic module 9. The cover 2 can cover an at least partially roundedopening of the fluidic chamber 1. The opening can be substantially fullycircular facilitating the detection of the cover in a pressurized stateand establishment of a gentle curvature of the cover. The fluidic module9 can be part of a disposable unit of the medical fluid delivery systemthat can be attached to the reusable unit.

In FIG. 1 a, the fluidic chamber 1 can be in a non-pressurized state,which can mean the pressure value in the chamber can correspond tonormal operation of the medical fluid delivery system. The deformablecover 2 cannot be deflected but can stretch planar over the fluidicchamber 1. The incident light beam 4 can be reflected on the planarsurface of the deformable cover 2 such that the reflected light beam 6can be directed on the first photodiode 5 a of the sensor unit 5. Thephotodiode 5 a can send a signal to an electronic control system (notshown) of the medical fluid delivery system to indicate a normalpressure condition within the fluidic path.

In FIG. 1 b, the fluidic chamber 1 is shown in a pressurized state. Asshown, the pressure within the fluidic chamber 1 increased such that thedeformable cover 2 can be deformed and can form an inflexion point area12 within the cover surface covering the fluidic chamber. The deformedcover 2 can have a convex shape with respect to the optical detectionsystem and the reusable unit respectively when the pressure within thefluidic path increases. The incident light beam 4 emitted by the lightemitter 3 can be directed on the cover 2 such that the incident lightbeam 4 can be reflected essentially in the inflexion point area 12, suchas, for example, in the inflexion point. The reflected light beam 6′ canbe deflected due to the change in orientation of the deformable cover 2in respect to the non-deformed cover by a distance s. The reflectedlight beam 6′ can now be directed on the second photodiode 5 b of thesensor unit 5. The photodiode 5 b can send a signal to the electroniccontrol system indicating a pressure change in the fluidic chamber 1and, therefore, in the fluidic path.

In FIGS. 2 a-c, the change in reflection of the incident light beam 4due to the deformation of the cover 2 is explained. In comparison to thenormal non-pressurized state, in the pressurized state, the deformablecover can be lifted translational by a height w, as shown in FIG. 2 a.That can mean the reflected light beam can be shifted and offset by adistance s₁, which can be defined by s₁=2·w·cos (α), wherein a can bethe incident angle between the incident light beam and the deformablecover. The reflected light beam 6′ of the pressurized state can beshifted from the first photodiode 5 a in the direction of the secondphotodiode 5 b by the distance s1. Also the deformable cover 2 can betilted by an angle ε relative to the non-pressurized state, which canchange the incident angle of the incident light beam, as shown in FIG. 2b. In the inflexion point area, the curvature of the deformed cover canchange. The surface of the deformed cover can be approximately even andthe angle ε can be approximately constant in this area. The direction ofthe reflected light beam can be changed by an angle δ, which can bedefined by δ=2·ε. That can lead to a shift s₂ on the sensor unit 5 fromthe first photodiode 5 a in the direction of the second photodiode 5 b,wherein s₂=d·tan (2ε) and d can correspond to the distance between thereflection point on the deformed cover and the sensor unit 5. As shownin FIG. 2 c, the total shift s of the reflected light beam 6 of thenon-pressurized state to a reflected light beam 6′ of the pressurizedstate by a deformation of the cover 2 can be given by s=s₁+s₂.

This can correspond to a linear mode of calculation, wherein the totalshift s can be linear in relation to the pressure in the fluidic chamber1 approximately. Of course more sophisticated calculation modes may beused. Also the mode of calculation can be based on a point-shaped lightbeam. In practice, in particular when using an LED as light emitter 3,the light beam can be a bundle of parallel light beams comprising adiameter D_(lb). For using the calculation, the beam diameter D_(lb) canbe selected such that light at the edge of the bundle does not extendover the center point of the deformable cover 2. The maximum bundlediameter D_(max) can fulfill the following requirement: D_(lb)≦0.58 sin(α) D_(cov), wherein D_(cov) can be the diameter of the deformable cover2. The diameter D_(cov) can be measured from a center point of thedeformable cover in direction of the inflexion point area chosen forreflecting the incident light beam.

The dual-element sensor 5 can generate two separated singular rawsignals S₁ and S₂, one signal S₁ of the photodiode 5 a and a secondsignal S₂ of the photodiode 5 b. In the case of a point-shaped lightbeam, for example, as emitted by a laser diode, the dual element sensorcan generate a binary sensor signal S that is one of the raw signals canbe on and the other one of the raw signal can be off. This can bebecause only one of the photodiodes 5 a and 5 b can be energized by thepoint-shaped light beam at a time. When using a LED as light emitter 3comprising a bundle of parallel light beams with a diameter D_(lb) agradual shift from one photodiode 5 a to the other photodiode 5 b canoccur.

FIG. 3 a illustrates the characteristics of the raw signals S₁ and S₂and a differentiation signal S when a center of the beam bundle isshifted from one center point on photodiode 5 a to the adjacent centerpoint on photodiode 5 b during deformation of the cover 2. The y-axiscan indicate the value of the sensor signals and the x-axis can indicatethe position of the center of the light bundle on the sensor 5. Whilethe beam bundle is centered on the first photodiode 5 a, raw signal S₁can have the value 1 and raw signal S₂ can have the value 0. During thedeformation of the cover 2, the beam bundle can wander to the center ofthe second photodiode 5 b, where raw signal S₁ can have the value 0 andraw signal S₂ can have the value 1. By differentiation S₂−S₁ of the tworaw signals, the sensor signal S can be extracted, which can besufficiently linear in the area of transition between the twophotodiodes. Such calculation model can allow a quantitativedetermination of the pressure values in the fluidic chamber.

In practice, the exact development of the sensor signal S and thebehavior of the reflected light beam can depend on the relativepositioning between the disposable unit and the reusable unit. Thepositioning usually can lie within a tolerance of about ±0.2 mm and maybe different for each disposable unit. Therefore, after placing a newdisposable unit on the reusable unit the sensor signal S can be taken asa reference value, wherein the fluidic pressure on the deformable covercan be about 0 bar relative to the atmosphere. The reference value canallow the integration of the absolute position of the cover beforestarting the operation of the medical fluid delivery system in thecalculation model. Afterwards, the usual operation of the system canstart, for example, by priming the fluidic path of the system withfluid.

In case the sensor device is used as an occlusion sensor for detectingocclusion of the fluidic path, for example, for a medical fluid deliverysystem or an infusion pump device, a characteristic occlusion thresholdvalue can be defined indicating an occlusion. In an algorithm, thethreshold value may be defined as a fixed value. Alternatively, thethreshold value of the differentiation sensor signal can be a functionof the reference value. Thus, an influence of disturbing factors, liketemperature effects or tolerance variations, can be minimized, which canmean the threshold value corresponding to occlusion can vary as littleas possible. One possibility can be to calculate the threshold value ofthe differentiation sensor signal for each disposable unit at thebeginning of the use of the disposable unit by involving the referencevalue and finally save the threshold value as fixed value. Again thecharacteristics according to FIG. 3 a can be used to describe the sensorsignal S. An expected shift s of the reflected light beam, which cancorrespond to an occlusion, can be known. Therefore based on thereference value, the expected shift s and the characteristics of thesensor signal S, the threshold value of the differentiation sensorsignal for the occlusion can be determined as shown in FIG. 3 b. Thecorresponding occlusion requirement can be:S ₂ −S ₁≧(S ₂ _(—) ₀ −S ₁ _(—) ₀)+m·swherein S₁ can be the raw signal of the first photodiode, S₂ can be theraw signal of the second photodiode, S₁ _(—) ₀ can be the referencevalue of the first photodiode at about 0 bar, S₂ _(—) ₀ can be thereference value of the second photodiode at about 0 bar, m can be theinclination of the characteristics of the sensor signal S in a linearrange, and s can be the expected shift of the reflected light beam onthe sensor unit.

Another possibility to determine the threshold value of thedifferentiation sensor signal can be to save the reference value of thespecific disposable unit and calculate the threshold value at the timeof detection.

Non-linear effects in determining an occlusion threshold value can beminimized for example by involving results of experimentalinvestigations. Experiments have shown that a required correction of athreshold value can be bigger, the higher the difference between areference value and a nominal value corresponding to an ideal situationis. One possible algorithm for defining an occlusion pressure valuebased on experimental investigations can involve only the referencevalue S₁ _(—) ₀ of the first photodiode and can be described by ahyperbolic relation as follows:S ₂ −S ₁≧(a/S ₁ _(—) ₀)+cwherein a can correspond to an empirical weighting and c can correspondto an offset value. The weighting factor a can minimize unwantednon-linear factors in the relevant range of the sensor signalcharacteristics. The offset value c can control the desired thresholdvalue. The weighting factor a and the offset value c can have a specificdesign of the sensor device taking into account different basicconditions, such as, for example, thickness of the cover, diameter ofthe cover, reflectivity of the cover, and the like. Generally, thethreshold value for an occlusion can be within the range of about 300mbar and about 1500 mbar. Furthermore a temperature factor can be takeninto consideration. A temperature sensor can be used to determinetemperature changes, which can be located close to the interface betweenthe disposable and reusable unit. Alternatively, a forward voltage ofthe LED may be used as temperature sensitive value.

In FIGS. 4 to 8, different embodiments of a sensor device are shown,wherein a light emitter 3 does not focus an incident light beam 4directly on the deformable cover 2 but one or more optical elements canbe, for example, part of a disposable unit of a medical fluid deliverysystem, which can deflect the light beam 4′ of the light emitter and candirect it as the incident light beam 4 in a predetermined angle on thedeformable cover. The incident light beam may reach the deformable coverin an angle between about 30° and about 60° or, in another embodiment,in an angle between about 40° and about 50°. Furthermore, an opticalelement can be in an optical path from the inflexion point area 12towards one or both of first and/or second photodiodes. These opticalelements can deflect the reflected light beam 6 of a non-pressurizedstate and the reflected light beam 6′ of a pressurized state such thatthey can be directed to the sensor unit. The optical elements may beseparate elements or realized in an optical unit including severaloptical elements. The material of the optical elements or unit can bemostly transparent, for example, an amorphous polymer may be used.Advantageously, the optical elements or unit can be made of the samematerial as the fluidic module 9. In general, the optical elements orunit can be adjusted relative to the deformable cover 2. Such opticalelements or units may be used in combination with light emitters 3,which can be in a reusable unit of a medical fluid delivery system andcan emit light beams perpendicular to the deformable cover 2. On thereflection side, the reflected light beams may be deflected by theoptical elements or unit such that the reflected light beam canperpendicularly enter the reusable unit or the optical window 8 thereof.

Using optical elements can allow that the transition of the light beamsbetween a disposable and a reusable unit of a medical fluid deliverysystem can be generally perpendicular, which can facilitate positioningof disposable and reusable unit relative to each other, in particularalong an orientation perpendicular to the interface surfaces.Furthermore, the optoelectronic parts of the sensor device, like thelight emitter and the sensor unit, can be in the reusable unit and canalso be in small and narrow constructions of a reusable unit.

In general, it can be possible to select only a part of the lightemitted by the light emitter 3, which can correspond to the directionfocusing on the inflexion point area 12 of the cover 2. Thus, thelateral position of the disposable unit relative to the reusable unitalong the surface of the deformable cover can allow more flexibility andtolerances can be larger. For example, a light-shaping element may beused to confine the emitted light beam.

In FIG. 4, a first embodiment of a sensor device is shown using anoptical unit 13 to direct the incident and the reflected light beams toand from the inflection point area 12 of the deformable cover 2. Thelight path of the light beam according to a non-pressurized state isshown as a solid line. The light beam 4′ emitted by the light emitter 3can enter the optical unit 13 perpendicularly and can be reflected at anoptical element 14 within the optical unit 13 comprising an angledreflection surface, such that an incident light beam 4 can exit theoptical unit 13 at an angle α towards the deformable cover 2. A minoroptical element can be used, for example. An exiting surface 15 can beorientated perpendicular to the incident light beam 4. Alternatively,the surface can be a refracting optical element and such can contributeto the alignment of the incident light beam. The incident light beam 4can be reflected at the inflexion point area 12. The reflected lightbeams 6 and 6′ can be directed back to the optical unit 13, can enterthe optical unit 13 generally perpendicular and can be reflected at asecond optical element 14′ within the optical element 13. The reflectedlight beam 6″ according to a non-pressurized state can be reflected onthe optical element 14′, can exit the optical element 13 and canperpendicularly meet the first photodiode 5 a of the sensor unit 5. Thelight path according to a pressurized state is shown as pointed line.The deformation of the deformable cover 2 can deflect the reflectedlight beam 6′. Therefore, the reflected light beam 6′ can be reflectedat the optical element 14′ offset from the reflected light beam 6 andcan be guided towards the photodiode 5 b as reflected light beam 6′″.

In FIG. 5, a second embodiment of a sensor device is shown, which issimilar to one of FIG. 4. But the optical elements for guiding the lightbeams can be separated from each other instead of being part of anoptical unit 13. A first optical element 14 can be used to reflect thelight beam 4′ of the light emitter 3. A second optical element 14′ canbe used to reflect the reflected light beam 6 in direction to photodiode5 a. And a third optical element 14″ can be used to reflect the shiftedreflected light beam 6′ in direction to photodiode 5 b. The singleoptical elements 14, 14′ and 14″ can be oriented individually from eachother.

In FIG. 6, a third embodiment of a sensor device is shown, which cancomprise an optical unit 13 with optical elements 14 and 14′ in form ofa convex free-forming surface. A bundle of light beams 4′ emitted by thelight emitter 3 can be reflected at the optical element 14 andsimultaneously the bundle of light beams 4′ can be focused on theinflexion point area 12 on the deformable cover 2 by the convex form ofthe free forming surface. The reflected light beams 6 and 6′ can bereflected at the convex free-forming surface of the optical element 14′.Due to the convex form the reflected light beam 6″ (non-pressurizedstate) and also the reflected light beam 6′″ (pressurized state) can runparallel to each other and perpendicular to the sensor unit 5. The angleγ at the reflection point of the optical element 14′ to focus thereflected light beams 6″ and 6′″ on the sensor unit 5 can be for exampledefined as γ=45°−½ (α+δ).

The sensor devices as shown in FIGS. 7 and 8 can be advantageously usedfor the detection of an occlusion of a medical fluid delivery system.The reflected light beam reflected from the deformable cover 2 can bedeflected at an optical element in largely different directions for areflected light beam 6 reflected at a non-deformed cover 2 and for areflected light beam 6′ reflected at a deformed cover 2. That can meanthe photo-elements 5 a and 5 b of the dual-element sensor 5 can bearranged individually and apart from each other.

In FIG. 7, the incident light beam can be directed to the deformablecover 2 as shown in FIG. 5. The reflected light beams 6 and 6′ can bedirected to an angled optical element 14′ comprising two reflectingplanes, which can be orientated in an angle towards each other. In anon-pressurized state, the reflected light beam 6 can be directed to afirst plane of the optical element 14′, which can reflect the reflectedlight beam 6″ to the photodiode 5 a. In a pressurized state, thereflected light beam 6′ can be directed to a second plane of the opticalelement 14′, which can reflect the reflected light beam 6′″ to thephotodiode 5 b. The reflected light beams 6″ and 6′ can be nearlydirected in opposite directions. The angle between first and secondplane may be in a desired location of the photodiodes 5 a and 5 b oraccording to space requirements in the reusable unit.

In FIG. 8, the incident light beam can be directed to an optical unit13, which can comprise an optical element 14′ in the form of an opticalsurface, which can act as a refraction surface for reflected light beamsreflected in a non-deformed state of the deformable cover 2 and can actas a reflection surface for reflected light beams reflected in adeformed state of the deformable cover 2. In particular, the opticalsurface may be designed such that the reflected light beam can bereflected at the optical element 14′ as soon as the deformation of thedeformable cover 2 can correspond to the occlusion threshold valueindicating an occlusion condition of the fluidic module 9. Also thesensor unit 5 may comprise a third photodiode, which can be energized bya light beam reflected on the deformable cover 2 in a state in betweenthe non-pressurized state and the pressurized state and can be refractedat the optical surface in direction of the third photodiode.

In FIGS. 9 and 10, sensor devices for use in a medical fluid deliverysystem are shown, wherein optical elements 14 and 14′ can be part of acap or covering 16 of the fluidic module 9, which can be attached to asurrounding edge 17 of the fluidic module. As shown in FIG. 9, thecovering 16 can extend between the optoelectronic parts arranged in thereusable unit of the medical fluid delivery system and the deformablecover 2 and can stretch between the edges 17. In the direction towardsthe deformable cover 2, the covering 16 can be designed according to anoptical unit as shown in FIG. 4 or 6 respectively and can provideoptical elements 14 and 14′ to direct the incident light beams 4 and 4′and the reflected light beams 6, 6′, 6″ and 6′″.

In FIG. 10, an embodiment of the sensor device is shown, wherein thelight emitter 3 can emit a light beam 4′ and the sensor unit 5 canreceive reflected light beams 6″ and 6′″ parallel to cover 2. That canmean the optoelectronic parts in the reusable unit can be located on aside of the disposable unit instead of opposite to it. The fluidicmodule can comprise optic elements 14 and 14′, wherein a first prism 14can direct the light beam 4′ of the light emitter 3 as an incident lightbeam 4 on the inflexion point area 12 of the deformable cover 2 and asecond prism 14′ in the form of a double prism can direct the reflectedlight beams 6″ and 6′″ to the sensor unit 5. The prism 14′ can bedesigned such that the light beam 6 reflected in a non-pressurized stateof the deformable cover 2 can be directed to the photodiode 5 a and thelight beam 6′ reflected in a pressurized state of the deformable cover 2can be directed to the photodiode 5 b.

It is noted that terms like “preferably,” “commonly,” and “typically”are not utilized herein to limit the scope of the claimed embodiments orto imply that certain features are critical, essential, or evenimportant to the structure or function of the claimed embodiments.Rather, these terms are merely intended to highlight alternative oradditional features that may or may not be utilized in a particularembodiment of the present disclosure.

For the purposes of describing and defining the present disclosure, itis noted that the term “substantially” is utilized herein to representthe inherent degree of uncertainty that may be attributed to anyquantitative comparison, value, measurement, or other representation.The term “substantially” is also utilized herein to represent the degreeby which a quantitative representation may vary from a stated referencewithout resulting in a change in the basic function of the subjectmatter at issue.

The present disclosure has been described in respect of severalembodiments of a sensor device. The present invention is not to belimited in scope by the specific embodiments described herein. Of coursethe features according to specific described embodiments may be combinedto further embodiments by a person skilled in the art although notexplained in detail herein. Indeed, various modifications of the presentinvention, in addition to those described herein, will be apparent tothose skilled in the art from the foregoing description and accompanyingdrawings. Thus, such modifications are intended to fall within the scopeof the appended claims. Additionally, various references are citedthroughout the specification, the disclosures of which are eachincorporated herein by reference in their entirety.

We claim:
 1. A sensor device for use in a medical fluid delivery system,the sensor device comprising: a fluidic chamber with a deformable coverclosing at least an area of the fluidic chamber, wherein, in apressurized state of the fluidic chamber, the deformable cover isdeformed such that it forms an inflexion point area within the deformedcover; and an optical detection system comprising at least one lightemitter for emitting one or more incident light beams and a sensor unitfor monitoring one or more reflected light beams, wherein the one ormore incident light beams emitted by the light emitter are directed onthe cover such that the one or more incident light beams are reflectedin the inflexion point area.
 2. The sensor device according to claim 1,wherein the one or more incident light beams are directed on the coverat an angle α.
 3. The sensor device according to claim 1, wherein thelight emitter of the sensor device is located on a side of the coverwhich is curved in a convex manner in an increased pressure state of thefluidic chamber.
 4. The sensor device according to claim 3, wherein oneside of the cover is in fluid contact and the light emitter is locatedon the other side of the cover.
 5. The sensor device according to claim1, wherein the incident light beam is a parallel light beam.
 6. Thesensor device according to claim 1, wherein the light emitter is a laserdiode comprising an optical element for parallelizing emitted lightbeams.
 7. The sensor device according to claim 1, wherein the lightemitter is a light emitting diode comprising an optical element forparallelizing emitted light beams.
 8. The sensor device according toclaim 1, wherein the sensor unit is a dual-element sensor with twophoto-elements.
 9. The sensor device according to claim 8, wherein anoptical element is provided in an optical path from the inflexion pointarea towards one or both of first and/or second photo-elements.
 10. Thesensor device according to claim 1, wherein a diameter of an overallincident light beam is selected such that an edge of the beam does notextend beyond a center point of the cover.
 11. The sensor deviceaccording to claim 1, wherein the cover covers an at least partiallyrounded opening of the fluidic chamber.
 12. The sensor device accordingto claim 1, wherein the one or more incident light beams are reflectedat an inflection point area located closest to the light emitter.
 13. Aninfusion pump device for use in a medical fluid delivery system, theinfusion pump device comprising a sensor device according to claim 1.14. A medical fluid delivery system, the medical fluid delivery systemcomprising a sensor device according to claim
 1. 15. The medical fluiddelivery system according to claim 14, wherein the optical detectionsystem is part of a reusable unit of the delivery device and the fluidicchamber is part of a disposable unit of the delivery device and whereinthe disposable unit comprises an optical element for directing theincident light beam in an angle α on the inflexion point area of thecover.
 16. The medical fluid delivery system according to claim 15,wherein the disposable unit comprises an optical element for directingthe reflected light beam from the inflexion point area to the sensorunit.
 17. A disposable unit for use with a medical fluid deliverysystem, wherein an optical element for directing an incident light beamof a sensor device in an angle α on an inflexion point area of adeformable cover of a fluidic chamber.
 18. A method for monitoring apressure change in a fluidic chamber of a medical fluid delivery systemusing a sensor device according to claim 1, comprising: directing one ormore incident light beams on the inflexion point area of the deformablecover; detecting one or more reflected light beams reflected from thedeformable cover in a non-pressurized state and a pressurized state; andcomparing detection data of the non-pressurized state and thepressurized state to extract the pressure change value.